The purpose of this study is to clarify the role of Galectin-3 (Gal3) on NSAIDs-induced intestinal ulcer. By using Gal3 knockout mice, we found that Gal-3 is a worsen factor of NSAIDs-induced intestinal ulcer. There are two possible mechanism for this negative effect of Gal3. The first one is a role of Gal3 as danger signal of activated macrophages. This molecule might cause sever inflammation. The another one is changes of intestinal bacterial flora with or without Gal-3. We found obvious differences of small intestinal flora population between wildtype mice and Gal3 mice. Those differences might affect to the ulceration by NSAIDs.